US2405848A - Lift truck - Google Patents

Description

G. QUAYLE LIFT TRUCK Aug 13, E94;

4 Sheets-Sheet 1 Filed Dec. 11, 1942 INVENTOR AT TO RNEY E3, wa,

G. QUAYLE LIFT TRUCK 1942 r 4 Sheets-Sheet 2 Filed Dec. ll

19464 G. QUAYLE. I 7 2,45; v -LIFT TRUCK INVEN-TOR ATTORNEY Aug. 13, 1946.

G. QUAYLE LIFT TRUCK Fil ed Dec. 11, 1942 4 Sheets-*SHeet 4 IN'YENTDR Gafg ATTORNEY Patented Aug. 13, 1946 LIFT TRUCK George Quayle, Philadelphia, Pa., assignor to The Yale & Towne Manufacturing Company, Stamford, Conn., a corporation of Connecticut Application December 11, 1942, Serial No. 468,715

25 Claims. 1

This invention relates to an industrial truck of the type having an elevating platform adapted to be raised relatively to a lifting head by the operation of a lifting mechanism.

More particularly my invention relates to a truck of the type disclosed in the Schroeder application 457,729, filed September 9, 1942, now Patent No. 2,367,061, dated January 9, 1945.

The industrial truck to which my invention is shown applied, is of that type having a lifting head and a platform that is pivoted at its forward end to the lifting head by upper and lower links, so that the platform may be elevated relatively to the lifting head by pivotal movement on the said links. The rear end of the elevating platform is supported by wheels that are pivoted to the platform on links, these links moving to raise the rear end of the platform as the forward end of the platform is elevated. The particular type of truck outlined is known in the art as a single frame truck, and it is to this type of truck that my invention is particularly applicable. However, as those skilled in art will readily appreciate upon the reading of the specification that follows, many features of my invention may be utilized in other types of industrial trucks, so that my invention should not be considered as limited to a single frame truck.

As one feature of my invention I employ a novel type of lifting link pivoted between the lifting head and the elevating platform, this link bein formed with a series of pins whereby the rotation of the link may be eifected through a lifting member that contacts the pins sequentially to rotate the link in step by step fashion.

A further feature of my invention resides in holding means for holding the elevating platform in each of its step by step positions and in its final fully elevated position. More in detail this feature of my invention resides in the mounting of a holding member preferably on the lifting link, with the holding member being adapted for cooperation with cooperative means on the lifting head whereby to hold the lifting link in each of its step by step lifting positions.

As a further feature of this part of my invention, I utilize a holding member in the form of a holding bar, or ratchet. bar preferably, this ratchet bar being pivoted to the lifting link for free swinging and cooperative engagement with a holding means on the lifting head.

A further feature of my invention resides in the holding means on the lifting head adapted for cooperation with the holdingmember or ratchet bar whereby to hold the elevating platform in its ele vated positions. As a more specific feature of my invention, the said holding means comprises a holding shaft, part of which is formed for cooperation with the holding bar or holding ratchet. It is a still further feature of my invention that the holding shaft may be rotated to n roll the ratchet bar out of holding relation therewith whereby to release the elevating platform for lowering movement.

A further feature of my invention resides in a novel form of treadle whereby the holding shaft is rotatable only after some predetermined movement of the treadle independently of the holding shaft. As a still further feature of my invention this predetermined movement of the treadle prior to rotation of the holding shaft, is adapted to effect the movement of the lifting means out of lifting engagement, it being a further feature of this part of my invention to contribute a'free handle to facilitate manipulation of the truck where the lifting means of the truck are actuated by the steering handle.

Still a further feature of my invention resides in means for normally maintaining the treadle in a position wherein the holding. means will be effective to hold the truck platform in its elevated position, with the treadle being adapted for movement automatically into position ,to, effect release of the holding means once the treadle is moved beyond a predetermined position in a direction to release the holding means. This feature of my invention is preferably obtained by me through the use of what I term a toggle spring arrangement, the toggle spring being adapted to urge and to maintain the treadle in one or the other of two extreme positions as soon as the treadle moves to one side or the other of a central or neutral position. Those skilled in the art will of course appreciate that this portion of my invention is of considerable utility in industrial trucks regardless of the types of lifting mechanism or holding means utilized.

As still a further feature of my invention I employ the lowering movement of the elevating platform to move the treadle beyond its neutral position as the elevating platform is lowered, whereby to restore the holding means to their holding position, thus enabling the operator to once again lift the elevating platform without requiring him to use manual means for re-setting his holding mechanism.

I have thus described the more important features of my invention in order that the operation of the structure of my invention may be better understood, Naturally, there are additional fea- 3 tures of my invention that have not been discussed generally but which will be readily understood upon a reading of the specifications that follow. Those skilled in the art will fully appreciate that the basic features of my invention, both those described and about to be described, may readily be utilized in specific forms other than 7 those forms that I shall herein show and describe.

Moreover, many of the features are useful and valuable per se as well as in combinations. It is therefore important that the patent claims granted me shall be sufficiently broad to prevent the appropriation of my invention by others in forms different from those whichI shall herein set forth.

For a description of my invention I shall refer to the drawings wherein Fig. l. is an elevation of an industrial truck to which my invention has been applied. Fig. 2 is a plan view of the truck of Fig. 1. Fig. 3 is a vertical section through the front end of the truck of Fig. 1. Fig. 4 is an enlarged view of certain of the parts shown in Fig. 3 to illustrate their action. Fig. 5 is a View similar .to Fig. 3 but showing the parts in a different position corresponding to full elevation of the elevating platform. Fig. 6 is a view of the parts of Figs. 3 and 5 but showing the platform being lowered. Fig. 7 is a view of certain of the parts of Fig. 6 illustrating the operation of those parts. Fig. 8 is a section taken along lines 8-8 of Fig. 3. Fig. 9 is a section taken along lines 9'.9 of Fig. 3.

Referring now more particularlyto the drawings and especially Figs. 1 and 2, the elevating platform of my truck is designated by reference numeral H} and is formed with a standard ll having a forward decorative portion l2 and a platform that is herein shown as formed of two legs l3 united at the rear by a cross bar M; The lifting head of my truck is shown in outline in Figs. 1 and 2- and the said outline is defined-by a series of reference numerals I5 so that the shape of the lifting head maybe perceived quite readily. Rotatable on a vertical bearing in the lifting head is what is termed a steering head it, to which is pivoted at- H' a steering handle assembly 4 supra, and is not per se my invention herein to be claimed.

Referring now more particularly to Figs. 3, 5, 6 and 8, the upper end of the standard I i is pivoted to the lifting head 15 by an upper link 35, this upper link being pivoted to the lifting head l5 through the shaft 36, and pivoted to the standard H. through the shaft 3'1. It is obvious that the upper link 35 and the lower link form between .themselves parallel arms for the movement of the elevating platform relatively to the lifting 18. The steering head it is adapted to rotate relatively to the lifting head l5 and has a pair of steering wheels l9, it being a function of the steering handle l8 to rotate the steering head i6 and; its wheels H. The rear supporting wheels of the elevating platform are designated by reference numeral 26; These wheels are carried on an-axle which is secured to lifting links 2| that are pivoted at 22 to the elevating platform l8 1 and are movable downwardly by rods 23 as the rods 23 move. to the right. The forward end of the elevating platform is pivoted at 24 to lower links 25 that are in turn pivoted at 26 to the lifting head l5. The rods 23 are pivoted at 21 to the links 25 so that as the elevating platform is raised on the links 25 the rods 23 will rotate the links 2| to raise the rear end of the platform.

A dashpot 3,0 i pivoted at 3! to the liftin head it, and at 32. to the standard H of the elevatingplatform Ill whereby to. control th 1owering movement of the elevating platform relatively to the lifting head, all as will be understood to those skilled in the art. It will be well to indicate at this point that the truck construction so far outlined in this application is that type of construction that is now manufactured by The Yale & Towne Mfg. Co. owner of this application endownerof the Schroeder application head. The upper link is of novel form per se, and is part of a novel combination of elements as will be seen presently.

There is secured to the link 35 a series of pins 38 called lifting pins, and for cooperation with these lifting pins I utilize what I term a lifting pawl 39 having a specially formed portion 40 for coaction with the pins 38. The lifting pawl 39 is itself pivoted at 90 to a lifting lever M that is pivoted at 42 on the lifting head iii. A spring 23 is secured at Ad to the lifting pawl 39 and at 9| to the lifting lever 41 and tends to urge the pawl 39 so that its surface 40 engages the pins 38 as shown in Fig. 3.

For rotating the lifting lever 41 on its pivot 42, I use a strut as that is bifurcated at 46 for cooperation with a pin 4'! of the lifting handle assembly 18. The upper end of the strut has a universal bearing at 48 relatively to the lifting lever ll, so that in all steering positions of the lifting handle 18, it is adapted through vertical reciprocation on its pivot H to rotate the lifting lever M. It is obvious that the particular movement will actuate the lifting pawl 39 to rotate the link 35 through pins 38.

For holding the elevating platform in each of its intermediate elevated positions and in its final elevated position I utilize a holding bar or holding ratchet, as it may be called, designated by reference numeral 50. The holding ratchet 50 is pivoted at 5| to the lifting link 35 so that it has considerable mechanical advantage, being displaced a relatively greater distance than pivot shaft 37 from the pivot shaft 36 about which the link 35'is pivoted on lifting head I5. The several ratchet teeth 52 of the ratchet bar 56 are adapted for cooperation with the flattened portion 54 of the holding shaft 55, and in Fig. 5 the lowermost tooth 52 of the ratchet bar 59 is shown in cooperative engagement With the holding shaft 55 for holding the lifting link 35 in'its fully elevated position. Through the ratchet bar 55 the platform is thus held in its fully elevated position.

The. holding shaft 55 (Fig. 9) is supported in bearings 55 and 51 relatively to the lifting head l5 and is adapted for rotation by a treadle 58 through a novel type of lazy connection, it being the. purpose of the saidlazy connection to allow the treadle 58 to move a predetermined distance before it imparts movement to the holding shaft 55. It is. obvious that rotary movement of the holding shaft 55 will be adapted to roll the ratchet bar 50 away from its position of Fig. 5 and into the position of Fig. 6.v In Fig- 6 there is best shown the positioning of the parts as the platform moves downwardly into its fully lowered position of Fig. 3 after being released for lowering movement. g

I shall now describe. the lazy connection between the treadle 58 and the holding shaft 55. The treadle 58 is formed with a corrugated portion 60 on which may be'placed the foot of the operator to depress the treadle as will be readily seen. The treadle has a bore Gltherethrough whereby it may be-mounted for free rotation on the holding shaft 55. An arm 82, as may best be seen from Fig. 9, is integral with the treadle 58 and is-laterally off-set from the main portion of the treadle, forming with said treadle and connecting bar 63 a U shaped member. What I term a ratchet cam 64 extends from the bar' 63 of the treadle 58 and also forms an integral part of the said treadle. A pin 85 traverses a bore 61 of treadle 58, this bore being somewhat larger in diameter than the bore 56 in the treadle shaft 55, and also larger in diameter than the pin 65. Because of this relationship of pin 65 to the bore 67 of the treadle 58, the treadle 58 may rotate from its full line position in Fig. 4 to itsdash and dot line position in Fig. 4 before the surfaces of the bore 61 contact the pin 85 to rotate that pin. Therotation of thetreadle from its full line position of Fig. 4 to its dash and dot line position of Fig. 4 is thus free of the shaft 55, and only thereafter will the continued rotation of the treadle 58 effect the rotation of the shaft55.

This lazy action of the treadle 58 relatively to the holding shaft 55 is utilized by me to move the lifting pawl 39 away from lifting engagement-with one of the pins 38 whereby to contribute what is termed in the art a free handle. Thus, those skilled in the art will fully appreciate-that in the position of the parts in Fig. 5 the lifting pawl 39 is held away from the lowermost pin 38 so that the lifting handle [8 may move freely without in any way being influenced bycontact of the lifting pawl 39 with the lowermost'pin 38. This movement of the pawl 39 to the position of Fig. 5 is contributed by treadle 58 through its arm 62 and a lever 18 pivoted at Tl to the lifting head l5. Thus, when the treadle 58 is moved from its full line position of Fig. 4 to its dotted line position of Fig. 4, which isthe same as its full line position of Fig. 5, the arm 62 contacts the lever 10 and rotates that lever 18 so that the part 18a of the saidlever contacts portion 39a of lifting pawl 39 and effects the rotation ofthe pawl 39 against the pressure of spring 43 into the position of Fig. 5. This movement of the lifting pawl 39 may be effected by the treadle 58 when the platform and the lifting link 35 are in the fully lowered position of Fig. 3 or in the fully-elevated position of Fig. 5.

It is obvious, of course, that this movement of the treadle 58, due to the lazy connection with holding shaft 55, has not rotated the holding shaft 55. This is very important because it is frequently desirable that when the platform is inits fully raised position, as in Fig. 5, the lifting pawl be released from the pin 38 of lifting link 35 while the holding ratchet 58 remains in holding engagement with the holding shaft 55. Further rotation of the treadle 58 from its dash and dot line position of Fig. 4 or its full line position of Fig. 5, will rotate the'holding shaft 55 from its position of Fig. 5 to its position of Fig. 6 whereby to effect a rolling or camming of the holding ratchet bar 50 away from the holding shaft 55 as will be quite readily apparent. The cam 64 that is integral with the treadle 58 is effective to contact the holding ratchet bar 50 to insure its movement from its position of Fig. 5 to its position of Fig. 6 in the event that the holding shaft is incapable of rolling or camming the ratchet bar out of its holding position of Fig. 5.

. The treadle 58 is normally maintained in its position of Figs. 3 and 4 by a toggle spring that fits about a toggle rod 76, the said toggle rodbeing slidable through an opening 11 in the lifting head l5 as is readily seen in Figs. 4, 6 and 7. The upper end of the toggle rod 18 is pivoted at 18 to the treadle 58 and a disc 19 fits about the toggle rod 15 and accepts the pressure of the toggle spring 15. So long as the parts are in the position of Figs. 3 and 4 the spring 15 will continue to maintain the parts in that position and the treadle shaft pin 85 will contact a limit pin for limiting the rotation of the treadle 58 and shaft 55 by the spring 15. Should the treadle be depressed so as to move the toggle rod it somewhat to the left of Fig. 4 and beyond a dead center position, the spring 15 will then act to rotate the treadle 58 in a clockwise direction to bring it against the limit pin 88 as seen in Fig. 7. In other words, the toggle spring 15 is effective through the toggle rod l5 and the remaining parts set forth to press the treadle into one or the other of the two extreme positions of Figs. 4 and 7, depending on the positioning of the treadle on one side or the other of a dead center position.

Because of the particular arrangement set forth, once the operator presses the treadle 58 from the position of Figs. 3 and 4 and somewhat beyond the dead center position of the toggle spring 15 and the toggle rod 15, the toggle spring l5 will thereafter press the treadle into its release position of Fig. 7 and will maintain it in that release position thereafter. Because of this construction of the parts, the operator need not hold his foot on the treadle until the platform is lowered in order to insure the continued lowering of the platform. The operator needs only to depress the treadle beyond a particular point and it thereafter remains fully depressed until the elevating platform is fully lowered.

As may be seen in Figs. 3 to '7 inclusive, a lug 82 is secured to the elevating platform standard 3 i and is adapted to contact the surface 83 of the treadle 58 when the platform is lowered. The lug 82 is effective to rotate the treadle 58 from its position of Fig. '7 to a position beyond the dead center position of the treadle 58 and the toggle rod it, so that the toggle spring '55 may thereafter rotate the treadle 58 to its initial position of Fig. 3. The effect of this action is of course to restore the treadle 58 and the holding shaft 55 to the initial holding position of the parts so that the operator may then proceed to elevate the platform without requiring his operation of any of the parts. This arrangement for automatically restoring the parts is of great utility in the hand lift truck'industry. Under some conditions the toggle spring '15 may be of only sufiicient strength to hold the treadle 58 yieldingly in its extreme positions after it is moved to said positions, all as is quite apparent.

It is Well to emphasize at this point that the treadle 58, in its normal operation, is adapted first to release the lifting pawl 33 from the pins 38 of the lifting link 85, and thereafter to release the holding means including the holding ratchet bar 58 and the holding shaft 55. Because of this arrangment of the parts, it is absolutely impossible to obtain what is knoWn in the industry as a flying handle; that is, a handle that is adapted to fly upwardly upon the application thereto of the weight of the elevating platform. It will also be well for a better understanding of the invention to indictae that the lifting link 35 is formed with a shoulder 85, best seen in Figs. 3 and 5, for engagement with a shoulder tion the lifting head' t tov form. anupper limit to the elevation of the platform relatively to the lifting head. Similarly, a shoulder 31 on the lifting link 35 contacts a connecting bolt 88 on the lifting head to denote the lower limit of. the elevating platform and the lifting link 35. It will be well also to indicate that a spring 89 is utilizedto prevent the flying movement of the holding ratchet bar 50 during the lowering'movement of the truck should that ratchet bar tend to flyupwardly from contact with the holding shaft 55 or the ratchet cam M.

It will now be obvious thatv vertical swinging movement of the lifting handle [8 is adapted, through the lifting lever 41, to efiect reciprocation ofthe lifting pawl 39 and through that pawl to rotate the lifting. link 35 from its position of Fig. 3 to its position of Fig, 5, thereby raising the elevating'platform Hi. Itlwill also be obvious that theholding ratchetbar. 5i) will cooperate with the holding shaft 55 to maintain the elevating platform raised. Rotation of, the treadle 58 is then effective to move the lifting'pawl 39 out oflifting engagement with any one of the pins 38 of the lifting link to contribute a free handle I8. Further rotation of the treadle is effective through pin 65 to rotate shaft 55 and effect a release of the holding ratchet bar 50 from, the holding shaft 55- to allow lowering movement of the elevating platform. The lowering of the elevating platform restores treadle 53 to its initial, position as lug 82 contacts surface 83. The automatic operation of the toggle rod and its toggle spring T5 for controlling the treadle 58 will. be clearly understood from the explanation already given.

I now claim:

,1. In a truck of th class described, a wheel supported lifting head, an elevating platform wheel supported at its rear end, a link pivoted by spaced pivots to said elevating platform and to said lifting head, a lifting device pivoted directly to both the platform and the lifting head on pivots spaced on a line parallel to the pivots of said link, a series of pins on said lifting device extending laterally therefrom, and means movably mounted on said lifting head and adapted to engage said pins sequentially to actuate said lifting device to lift said platform.

2. In a truck of the class described, a wheel supported lifting head, an elevating platform wheel supported at its rear end, a link pivoted by spaced pivots to said elevating platform and to said lifting head, a lifting device pivoted directly to both the platform and the lifting head on pivots spaced on a line parallel to the pivots of said link, a series of pins on said lifting device extending laterally therefrom, a lifting pawl adapted to engage said pins sequentially to actuate said lifting device to lift said platform relatively to said lifting head, and means movably mounting said lifting pawl on said lifting head.

3. m a truck of the class described, a wheel supported lifting head, an elevating platform wheel supported at its rear end, upper and lower links pivoted at one end to said platform and at the other end to said lifting head whereby to assemble said head and platform while mounting said platform for upward pivotal movement on said lifting head, a series of pins extending laterally from one of said links, and a lifting member movably mounted on said lifting head and adapted to engage said pins sequentially to actuate said link to lift said elevating platform.

4.,In a truck of the class described, a lifting headian elevating platform, a lifting device pivoted directly to an integral portion of said lifting head and to an integral part of said elevating platform, means whereby step by step lift movement is imparted to said lifting device to lift said platform, a holdingmember pivoted to said lifting device, and a holding surface on said lifting head over which said holding member rides as said lifting device is moved step by step, said holding member having surfaces cooperable with said holding surface to hold said lifting device in each of its step by step positions. 7

5. In a truck of the class described, a lifting head, an elevating platform, a lifting device, means whereby said lifting device lifts said platform relatively to said lifting head, means whereby step by step lift movement is imparted to said lifting device to lift said platform, a holding member pivoted to said lifting device and hanging loosely downwardly therefrom, and a holding surface on said lifting head over which said holding member rides as said lifting device is moved step by step, said holding member having ,surfaces cooperable with said holding surface to hold said lifting device in each of its step by step positions.

6. In a truck of the class described, a lifting head, an elevating platform, a lifting device, means whereby said lifting device lifts said platform relatively to said lifting head, means whereby step by step lift movement is imparted to said lifting device to lift said platform, a holding ratchet pivoted at one end to said lifting device, and depending freely from said. pivoted end, a holding surface on said lifting head over which said holding ratchet rides as said lifting device is moved step by step, said holding ratchet having ratchet surfaces cooperable with said holding surface to hold said lifting device in each of its step bystep positions.

7. In a truck of the class described, a lifting head, an elevating platform, a lifting device, means whereby said lifting device lifts said platform relatively to said lifting head, means whereby step by step lift movement is imparted to said lifting device to lift said platform, a holding ratchet pivotally mounted at one end on said lifting device, and hanging freely from said pivotal mounting, a holding surface on said lifting head over which said holding ratchet rides as said lifting device is moved step by step, said holding ratchet having ratchet surfaces cooperable with said holding surface to hold said lifting device in each of its step by step positions, and means for rotating said holding surface whereby to roll said holding ratchet out of holding relation to said holding surface.

8. In a truck of the class described, a lifting head, an elevating platform, a lifting device, means wherebysaid lifting device lifts said platform relatively to said lifting head, means adapted to actuate said lifting device step by step to lift said elevating platform, a ratchet bar pivoted to said lifting device and hanging freely downwardly therefrom, a pawl surface over which said ratchet bar rides as saidlifting device is actuated, the ratchet teeth of said bar coasting with said pawl surface to hold. said lifting device in each of its step by step positions, a shaft of which said pawl surface is a part, and means for rotating said shaft to roll said pawl surface out of holding relation to the teeth of said ratchet bar.

9, In a truck of the class described, a lifting head, an elevating platform, a lifting device,

mechanical advantage relatively to the means of connection of said lifting device with said platform, said ratchet bar depending freely from said pivotal mounting and rotatable on said mounting, a pawl surface over which said ratchet bar rides as said liftingdevice is actuated, the ratchet teeth of said bar coacting with said pawl surface to hold said lifting device in each of its step by step positions, and means for rolling said. pawl surface out of holding relation to the teeth of said ratchet bar.

10. In a truck of the class described, a liftin head, an elevating platform, lifting means for lifting said elevating platform relatively to said lifting head, holding means for holding said elevating platform lifted relatively to said lifting head, a control shaft for controlling said holding means, a treadle rotatably mounted on said shaft, means operated by said rotatable treadle, and means whereby said treadle rotates said shaft after it rotates a predetermined degree relatively to said shaft.

11. In a truck of the class described, a lifting head, an elevating platform adapted to be lifted relatively to said lifting head,-a control shaft, a rotatable treadle, means whereby said treadle rotates said shaft after it rotates a predetermined degree relatively to said shaft, a lifting device participating functionally in the lifting a of the elevating platform relatively to said liftinghead, a holding device for holding said elevating platform lifted relatively to said lifting head, means whereby said treadle moves said lifting device, and means whereby said shaft moves said holding device.

12. In a truck of the class described, an elevating platform, a lifting head, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in its step by step lifted positions comprising a ratchet bar and a holding shaft, said holding shaft having a portion of its surface cut away to present a shoulder to the ratchet teeth formed on said ratchet bar, a treadle adapted to rotate said holding shaft to move said shoulder away from holding relation to said ratchet bar, and a lazy connection between said treadle and said shaft whereby said treadle moves a predetermined degree prior to rotating said shaft.

13. In a truck of the class described, an elevating platform, a lifting head, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in its step by step lifted positions comprising a ratchet bar and a holding shaft. said holding shaft having a portion of its surface cutaway to present a shoulder to the ratchet teeth formed on said ratchet bar, a treadle adapted to rotate said holding shaft to move said shoulder away from holding relation to said ratchet bar, and a lazy connection between said treadle and said shaft whereby said treadle moves a predetermined degree prior to rotating said shaft.

14. In a truck of the class described, a lifting head, an elevating platform, a lifting device, means whereby said lifting device lifts said platform relatively to said lifting head, lifting means '10 movably mounted on said lifting head and adapted to engage and then move said lifting device step by step to lift said elevating platform, a ratchet bar pivoted tosaid lifting device, a pawl surface over which said ratchet bar rides as said lifting device is actuated, the ratchet teeth of said bar coacting with said pawl surface to hold said lifting device in each of its step by step positions, a shaft of which said pawl surface is a part, a treadle for rotating said shaft'to move said pawl surface away from holding relation to said ratchet bar, and means whereby said treadle moves said lifting means away from engagement with said lifting device before it rotates said shaft.

15. In a'truck of the class described, an elevating platform, a lifting head, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in its step by step lifted positions comprising a ratchet bar and a holding shaft, means pivoting said ratchet bar to 'a part of said step by step lifting mechanism for movement therewith as said platform is lifted, said ratchet bar hanging freely from said part and riding over said shaft as it 'moves with said part, and said holding shaft having a portion of its surface cut away to present a shoulder to ratchet teeth formed on the surface of said ratchet bar.

16. In a truck of the class described, an elevating platform, a lifting head, holding means for holding said elevating platform in a lifted position relatively to said lifting head, a treadle for controlling said holding means, a toggle spring for maintaining said treadle in one position, and means whereby the movement of said treadle a predetermined distance from said position positions the spring so that it presses said treadle into a second position.

17. In a truck of the class described, a lifting head, an elevating platform, lifting means'for lifting said elevating platform relatively to said lifting head, holding means for holding saidlelevating platform lifted relatively to saidlifting head, a movable control treadle for controlling said holding means, a toggle spring for maintaining said treadle in one position, and means whereby the movement of said treadle a predetermined distance from said position positions the spring so that it presses said treadle into a second position.

18. In a truck of the class described, an elevating platform, a lifting head, holding means for holding said elevating platform in a lifted position relatively to said lifting head, a treadle for controlling said holding means, a toggle spring for maintaining said treadle in one position in which said means are positioned to hold said elevating platform in any position to which it is lifted, and means whereby the movement of said treadle a predetermined distance from said position positions the spring so that it presses said treadle into a second position in which said holding means are positioned to allow lowering of said platform.

19. In a truck of the class described, an elevating platform, a lifting head, holding means for holding said elevating platform in a lifted position relatively to said lifting head, a treadle for controlling said holding means, a toggle spring for maintaining said treadle in one position in which said holding means are positioned to hold said elevating platform in any position to which it is lifted, and means whereby the movement of said treadle a predetermined distance from said position positions the spring so that it presses said treadle into a second position,

in which saidholding means are positioned to allow lowering of said platform, and means whereby the lowering of said platform effects the movement of said treadle back towards said first position.

20. In a truck of the class described, a lifting head, a lifting platform, upper and lower links pivotally connecting the front end of said lifting platform to said lifting head to form a complete truck and to mount said lifting platform for lifting movement relatively to said lifting head,

wheel supporting links pivoted to the rear end of said platform, means whereby' the lifting movement of the front end of said platform relatively to said lifting head .moves said wheel supporting links to lift the rear .end of said platform, a movable lifting member mounted on said lifting head, means formed on one of said links engaged by said lifting member for moving said link whereby to lift the front end of said platform relatively to said lifting head, and .a holding member pivoted to said link and adapted to engage holding means on said lifting head for holding said lifting platform in its lifted position.

'21. In a truck of the class described, a liftin head, an elevating platform, lifting means for lifting said elevating platform relatively to Said lifting head, holding means for holding said elevating platform lifted relatively to said lifting head, a control shaft for controlling said holding means, a rotatable treadle for rotating said control shaft, means operated by said rotatable treadle, and means of connection between said control shaft and treadle whereby said treadle rotates said shaft after rotating a predetermined degree relatively to said shaft.

22. In a truck of the class described,an elevating platform, a lifting head, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in its step by step lifted positions, a control shaft, a rotatable treadle, means whereby said treadle rotates said control shaft after said treadle rotates a predetermined degree relatively to said control shaft, means whereby said treadle moves parts of said lifting mechanism out of engagement, and means whereby said control shaft releases said holding mechanism.

'23. In a truck of the class described, an elevating platform, a lifting head, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in its step by step lifted positions comprising a ratchet bar and a holding shaft, and a portion of said holding shaft, being cut away to present a shouldered portion to the ratchet teeth formed on said ratchet bar.

24. In a truck of the class described, an elevating platform, a liftinghead, a step by step lifting mechanism for lifting said elevating platform, a holding mechanism for holding said elevating platform in' its step by step lifted positions :comprising a ratchet bar and a holding shaft, a portion of said holding shaft being cut away to present a shouldered portion to the ratchet teeth formed on said ratchet bar, and means for rotating said holding shaft whereby to roll said ratchet bar away from said shouldered portion of said shaft.

25. In a truck of the class described, a lifting head, an elevating platform, lifting means for lifting said elevating platform relatively to said lifting head, holding means for holding said elevating platform lifted relatively to said lifting head, a control treadle rotatably mountedon a part of said truck for controlling said lifting and holding means, a toggle spring for pressing said treadle into one or the other of two extreme control positions, and means whereby said spring is positioned by rotation of said treadle whereby when said toggle spring and treadle are at one side of a predetermined position said toggle spring will press said treadle into one of said extreme positions, whereas when said treadle and spring are at the other side of said predetermined position said toggle sprlng will press said treadle into the other of said extreme positions.

GEORGE QUAYLE.

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